Olefin production process

ABSTRACT

A process is provided to stabilize and/or reactivate an olefin production catalyst system which comprises contacting an olefin production catalyst system, either before or after use, with an aromatic compound.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 08/951,201 filed Oct. 14, 1997, which isincorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

This invention relates to olefin production and olefin productionprocess improvements.

Olefins, primarily alpha olefins, have many uses. In addition to uses asspecific chemicals, alpha-olefins, especially mono-1-olefins, are usedin polymerization processes either as monomers or comonomers to preparepolyolefins, or polymers. These alpha-olefins usually are used in aliquid or gas state. Unfortunately, very few efficient processes toselectively produce a specifically desired alpha-olefin are known.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide an improvedolefin production process.

It is another object of this invention to provide an olefin productionprocess which will provide high purity 1-hexene.

It is a further object of this invention to provide an olefin productionprocess which can be used in conjunction with other processes thatutilize trimerization reaction reactants and/or reaction products.

In accordance with this invention, a process is provided to trimerizeolefins comprising, in combination a) a reactor, b) at least one inletline into said reactor for olefin reactant and catalyst system, c)effluent lines from said reactor for trimerization reaction products,and d) at least one separator to separate desired trimerization reactionproducts; wherein said catalyst system comprises a chromium source, apyrrole-containing compound and a metal alkyl.

In accordance with another embodiment of this invention, a process isprovided to trimerize ethylene comprising, in combination a) a reactor,b) at least one inlet line into said reactor for ethylene reactant andcatalyst system, c) effluent lines from said reactor for trimerizationreaction products, and d) at least one separator to separate desired1-hexene reaction product; wherein said catalyst system comprises achromium source, a pyrrole-containing compound, a metal alkyl, andoptionally a halide source.

In accordance with yet another embodiment of this invention, a processis provided to trimerize olefins consisting essentially of, incombination a) a reactor, b) at least one inlet line into said reactorfor olefin reactant and catalyst system, c) effluent lines from saidreactor for trimerization reaction products, and d) at least oneseparator to separate desired trimerization reaction products; whereinsaid catalyst system comprises a chromium source, a pyrrole-containingcompound and a metal alkyl.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, forming a part hereof, wherein like referencecharacters denote like parts in the various figures,

FIG. 1 is a schematic representation of one embodiment of an oleintrimerization process using four separators, wherein two of saidseparators are used following olefin removal.

FIG. 2 is a schematic representation of another embodiment of an olefintrimerization process using one separator after olefin removal.

FIG. 3 is a schematic representation of a further embodiment of anolefin trimerization process using a solventless trimerization reactionsystem.

FIG. 4 is a schematic representation of yet a further embodiment of anolefin trimerization process wherein reactant and trimerized product(s)are sent directly to an olefin polymerization unit.

FIG. 5 is a schematic representation of still another embodiment of anolefin trimerization process wherein catalyst system and reactor heaviesare removed after a separation sequence; other embodiments, such as, forexample, include use of two columns to separate trimerized product(s),as in FIG. 1, or a solventless system, as in FIG. 3, can be employed asvariations.

FIG. 6 is a schematic representation of yet another embodiment of anolefin trimerization process wherein catalyst system and reactor heaviesstream(s) can undergo further product separation. While these drawingsdescribe embodiments of the invention for the purpose of illustration,the invention is not to be construed as limited by the drawings but thedrawings are intended to cover all changes and modifications within thespirit and scope thereof.

DETAILED DESCRIPTION OF THE INVENTION Catalyst Systems

Catalyst systems useful in accordance with this invention comprise achromium source, a pyrrole-containing compound and a metal alkyl, all ofwhich have been contacted and/or reacted in the presence of anunsaturated hydrocarbon. Optionally, these catalyst systems can besupported on an inorganic oxide support. These catalyst systems areespecially useful for the dimerization and trimerization of olefins,such as, for example, trimerization of ethylene to 1-hexene.

The chromium source can be one or more organic or inorganic compounds,wherein the chromium oxidation state is from 0 to 6. Generally, thechromium source will have a formula of CrX_(n), wherein X can be thesame or different and can be any organic or inorganic radical, and n isan integer from 1 to 6. Exemplary organic radicals can have from about 1to about 20 carbon atoms per radical, and are selected from the groupconsisting of alkyl, alkoxy, ester, ketone, and/or amido radicals. Theorganic radicals can be straight-chained or branched, cyclic or acyclic,aromatic or aliphatic, can be made of mixed aliphatic, aromatic, and/orcycloaliphatic groups. Exemplary inorganic radicals include, but are notlimited to halides, sulfates, and/or oxides.

Preferably, the chromium source is a chromium(II)-and/orchromium(III)-containing compound which can yield a catalyst system withimproved trimerization activity. Most preferably, the chromium source isa chromium(III) compound because of ease of use, availability, andenhanced catalyst system activity. Exemplary chromium(III) compoundsinclude, but are not limited to, chromium carboxylates, chromiumnaphthenates, chromium halides, chromium pyrrolides, and/or chromiumdionates. Specific exemplary chromium(III) compounds include, but arenot limited to, chromium(III) 2,2,6,6,-tetramethylheptanedionate[Cr(TMHD)₃], chromium(III) 2-ethylhexanoate [Cr(EH)₃, also referred toas chromium(III) tris(2-ethylhexanoate),] chromium(III) naphthenate[Cr(NP)₃], chromium(III) chloride, chromic bromide, chromic fluoride,chromium(III) acetylacetonate, chromium(III) acetate, chromium(III)butyrate, chromium(III) neopentanoate, chromium(III) laurate,chromium(III) stearate, chromium(III) pyrrolides and/or chromium(III)oxalate.

Specific exemplary chromium(II) compounds include, but are not limitedto, chromous bromide, chromous fluoride, chromous chloride, chromium(II)bis(2-ethylhexanoate), chromium(II) acetate, chromium(II) butyrate,chromium(II) neopentanoate, chromium(II) laurate, chromium(II) stearate,chromium(II) oxalate and/or chromium(II) pyrrolides.

The pyrrole-containing compound can be any pyrrole-containing compound,or pyrrolide, that will react with a chromium source to form a chromiumpyrrolide complex. As used in this disclosure, the term“pyrrole-containing compound” refers to hydrogen pyrrolide, i.e.,pyrrole (C₄H₅N), derivatives of hydrogen pyrrolide, substitutedpyrrolides, as well as metal pyrrolide complexes. A “pyrrolide” isdefined as a compound comprising a 5-membered, nitrogen-containingheterocycle, such as for example, pyrrole, derivatives of pyrrole, andmixtures thereof. Broadly, the pyrrole-containing compound can bepyrrole and/or any heteroleptic or homoleptic metal complex or salt,containing a pyrrolide radical, or ligand. The pyrrole-containingcompound can be either affirmatively added to the reaction, or generatedin-situ.

Generally, the pyrrole-containing compound will have from about 4 toabout 20 carbon atoms per molecule. Exemplary pyrrolides are selectedfrom the group consisting of hydrogen pyrrolide (pyrrole), lithiumpyrrolide, sodium pyrrolide, potassium pyrrolide, cesium pyrrolide,and/or the salts of substituted pyrrolides, because of high reactivityand activity with the other reactants. Examples of substitutedpyrrolides include, but are not limited to, pyrrole-2-carboxylic acid,2-acetylpyrrole, pyrrole-2-carboxyaldehyde, tetrahydroindole,2,5-dimethylpyrrole, 2,4-dimethyl-3-ethylpyrrole,3-acetyl-2,4-dimethylpyrrole,ethyl-2,4-dimethyl-5-(ethoxycarbonyl)-3-pyrrole-proprionate,ethyl-3,5-dimethyl-2-pyrrolecarboxylate, and mixtures thereof. When thepyrrole-containing compound contains chromium, the resultant chromiumcompound can be called a chromium pyrrolide.

The most preferred pyrrole-containing compounds used in a trimerizationcatalyst system are selected from the group consisting of hydrogenpyrrolide, i.e., pyrrole (C₄H₅N), 2,5-dimethylpyrrole and/or chromiumpyrrolides because of enhanced trimerization activity. Optionally, forease of use, a chromium pyrrolide can provide both the chromium sourceand the pyrrole-containing compound. As used in this disclosure, when achromium pyrrolide is used to form a catalyst system, a chromiumpyrrolide is considered to provide both the chromium source and thepyrrole-containing compound. While all pyrrole-containing compounds canproduce catalyst systems with high activity and productivity, use ofpyrrole and/or 2,5-dimethylpyrrole can produce a catalyst system withenhanced activity and selectivity to a desired product(s).

The metal alkyl can be any heteroleptic or homoleptic metal alkylcompound. One or more metal alkyls can be used. The alkyl ligand(s) onthe metal can be aliphatic and/or aromatic. Preferably, the alkylligand(s) are any saturated or unsaturated aliphatic radical. The metalalkyl can have any number of carbon atoms. However, due to commercialavailability and ease of use, the metal alkyl will usually comprise lessthan about 70 carbon atoms per metal alkyl molecule and preferably lessthan about 20 carbon atoms per molecule. Exemplary metal alkyls include,but are not limited to, alkylaluminum compounds, alkylboron compounds,alkyl magnesium compounds, alkyl zinc compounds and/or alkyl lithiumcompounds. Exemplary metal alkyls include, but are not limited to,n-butyl lithium, s-butyllithium, t-butyllithium, diethylmagnesium,diethylzinc, triethylaluminum, trimethylaluminum, triisobutylalumium,and mixtures thereof.

Preferably, the metal alkyl is selected from the group consisting ofnon-hydrolyzed, i.e., not pre-contacted with water, alkylaluminumcompounds, derivatives of alkylaluminum compounds, halogenatedalkylaluminum compounds, and mixtures thereof for improved productselectivity, as well as improved catalyst system reactivity, activity,and/or productivity. The use of hydrolyzed metal alkyls can result indecreased olefin, i.e., liquids, production and increased polymer, i.e.,solids, production.

Most preferably, the metal alkyl is a non-hydrolyzed alkylaluminumcompound, expressed by the general formulae AlR₃, AlR₂X, AlRX₂, AlR₂OR,AlRXOR, and/or Al₂R₃X₃, wherein R is an alkyl group and X is a halogenatom. Exemplary compounds include, but are not limited to,triethylaluminum, tripropylaluminum, tributylaluminum, diethylaluminumchloride, diethylaluminum bromide, diethylaluminum ethoxide,diethylaluminum phenoxide, ethylaluminum dichloride, ethylaluminumsesquichloride, and mixtures thereof for best catalyst system activityand product selectivity. The most preferred alkylaluminum compound istriethylaluminum, for best results in catalyst system activity andproduct selectivity.

Usually, contacting and/or reacting of the chromium source,pyrrole-containing compound and a metal alkyl is done in an unsaturatedhydrocarbon and can be done in any manner known in the art. For example,a pyrrole-containing compound can be contacted with a chromium sourceand then with a metal alkyl. Optionally, a pyrrole-containing compoundcan be contacted with a metal alkyl and then with a chromium source.Numerous other contacting procedures can be used, such as for example,contacting all catalyst system components in the trimerization reactor.

The unsaturated hydrocarbon can be any aromatic or aliphatichydrocarbon, in a gas, liquid or solid state. Preferably, to effectthorough contacting of the chromium source, pyrrole-containing compound,and metal alkyl, the unsaturated hydrocarbon will be in a liquid state.The unsaturated hydrocarbon can have any number of carbon atoms permolecule. Usually, the unsaturated hydrocarbon will comprise less thanabout 70 carbon atoms per molecule, and preferably, less than about 20carbon atoms per molecule, due to commercial availability and ease ofuse. Exemplary unsaturated, aliphatic hydrocarbon compounds include, butare not limited to, ethylene, 1-hexene, 1,3-butadiene, and mixturesthereof. The most preferred unsaturated aliphatic hydrocarbon compoundis 1-hexene, because of elimination of catalyst system preparation stepsand 1-hexene can be a reaction product. Exemplary unsaturated aromatichydrocarbons include, but are not limited to, toluene, benzene, xylene,ethylbenzene, mesitylene, hexamethylbenzene, and mixtures thereof.Unsaturated, aromatic hydrocarbons are preferred in order to improvecatalyst system stability, as well as produce a highly active andselective catalyst system. The most preferred unsaturated aromatichydrocarbon is selected from the group consisting of toluene andethylbenzene, with ethylbenzene most preferred for best catalyst systemactivity and product selectivity, as well as ease of use.

Optionally, and preferably, a halide source is also present in thecatalyst system composition. The presence of a halide source in thecatalyst system composition can increase catalyst system activity andproductivity, as well as increase product selectivity. Exemplary halidesinclude, but are not limited to fluoride, chloride, bromide, and/oriodide. Due to ease of use and availability, chloride is the preferredhalide. Based on improved activity, productivity, and/or selectivity,bromide is the most preferred halide.

The halide source can be any compound containing a halogen. Exemplarycompounds include, but are not limited to, compounds with a generalformula of R_(m)X_(n), wherein R can be any organic and/or inorganicradical, X can be a halide, selected from the group consisting offluoride, chloride, bromide, and/or iodide, and m+n can be any numbergreater than 0. If R is an organic radical, preferably R has from about1 to about 70 carbon atoms per radical and, most preferably from 1 to 20carbon atoms per radical, for best compatibility and catalyst systemactivity. If R is an inorganic radical, preferably R is selected fromthe group consisting of aluminum, silicon, germanium, hydrogen, boron,lithium, tin, gallium, indium, lead, and mixtures thereof. Specificexemplary compounds include, but are not limited to, methylene chloride,chloroform, benzylchloride, silicon tetrachloride, tin(II) chloride,tin(IV) chloride, germanium tetrachloride, boron trichloride, aluminumtribromide, aluminum trichloride, 1,4-di-bromobutane, and/or1-bromobutane. Most preferably, the halide source is selected from thegroup consisting of tin (IV) halides, germanium halides, and mixturesthereof.

Furthermore, the chromium source, the metal alkyl and/or unsaturatedhydrocarbon can contain and provide a halide to the reaction mixture.Preferably, if a halide is present, the halide source is analkylaluminum halide and is used in conjunction with alkylaluminumcompounds due to ease of use and compatibility, as well as improvedcatalyst system activity and product selectivity. Exemplaryalkylaluminum halides include, but are not limited to,diisobutylaluminum chloride, diethylaluminum chloride, ethylaluminumsesquichloride, ethylaluminum dichloride, diethylaluminum bromide,diethylaluminum iodide, and mixtures thereof.

It should be recognized, however, that the reaction mixture comprising achromium source, pyrrole-containing compound, metal alkyl, unsaturatedhydrocarbon and optionally a halide can contain additional componentswhich do not adversely affect and can enhance the resultant catalystsystem.

Reactants

Trimerization, as used in this disclosure, is defined as the combinationof any two, three, or more olefins, wherein the number of olefin, i.e.,carbon-carbon double bonds is reduced by two. Reactants applicable foruse in the trimerization process of this invention are olefiniccompounds which can a) self-react, i.e., trimerize, to give usefulproducts such as, for example, the self reaction of ethylene can give1-hexene and the self-reaction of 1,3-butadiene can give1,5-cyclooctadiene; and/or b) olefinic compounds which can react withother olefinic compounds, i.e., co-trimerize, to give useful productssuch as, for example, co-trimerization of ethylene plus hexene can give1-decene and/or 1-tetradecene, co-trimerization of ethylene and 1-butenecan give 1-octene, co-trimerization of 1-decene and ethylene can give1-tetradecene and/or 1-docosene. For example, the number of olein bondsin the combination of three ethylene units is reduced by two, to oneolefin bond, in 1-hexene. In another example, the number of olefin bondsin the combination of two 1,3-butadiene units, is reduced by two, to twoolefin bonds in 1,5-cyclooctadiene. As used herein, the term“timerization” is intended to include dimerization of diolefins, as wellas “co-trimerization”, both as defined above.

Suitable trimerizable olefin compounds are those compounds having fromabout 2 to about 30 carbon atoms per molecule and having at least oneolefinic double bond. Exemplary mono-1-olefin compounds include, but arenot limited to acyclic cyclic olefins such as, for example, ethylene,propylene, 1-butene, 2-butene isobutylene, 1-pentene, 2-pentene,1-hexene, 2-hexene, 3-hexene, 1-heptene, 2-heptene, 3-heptene, the fournormal octenes, the four normal nonenes, and mixtures of any two or morethereof. Exemplary diolefin compounds include, but are not limited to,1,3-butadiene, 1,4-pentadiene, and 1,5-hexadiene. If branched and/orcyclic olefins are used as reactants, while not wishing to be bound bytheory, it is believed that steric hindrance could hinder thetrimerization process. Therefore, the branch and/or cyclic portion(s) ofthe olefin preferably should be distant from the carbon-carbon doublebond.

Catalyst systems produced in accordance with this invention preferablyare employed as trimerization catalyst systems.

Products

The olefinic products of this invention have established utility in awide variety of applications, such as, for example, as monomers for usein the preparation of homopolymers, copolymers, and/or terpolymers. Theolefinic products of this invention can have from about 6 to about 100carbon atoms per molecule. As discussed previously, trimerization ofethylene can yield hexenes, preferably 1-hexene. Trimerization ofethylene and 1-hexene can produce decenes, preferably 1-decene.Trimerization of 1,3-butadiene can produce 1,5-cyclooctadiene.

Drawings

A further understanding of some of the aspects of this invention can befound by referring to the attached schematic flow diagrams, incombination with the following descriptions. Various additional pumps,valves, heaters, coolers and other conventional equipment necessary forthe practice of this invention will be familiar to one skilled in theart. Said additional equipment has been omitted from the drawings forthe sake of clarity. The descriptions of the drawings provide one methodfor operating the process. However, it is understood that while thesedrawings are general representations of the process, minor changes canbe made in adapting the drawings to the various conditions within thescope of the invention. It is also understood that numerical referencesin the drawings are consistent throughout the drawings. For example,inlet line 1, an olefin and optionally hydrogen inlet line, is an olefinand optionally hydrogen inlet line in all drawings.

As used in this disclosure, “olefin feed” refers to compounds more fullydefined in the “Reactant” portion of this disclosure, such as, forexample, ethylene, propylene, and/or 1-hexene. “Solvent” refers to adiluent or medium in which the trimerization process occurs; however, byno means is the solvent necessarily an inert material; it is possiblethat the solvent can contribute to a trimerization reaction process.Exemplary solvents include, but are not limited to, cyclohexane,methylcyclohexane, isobutane, 1-hexene, and mixtures of two or morethereof. “Reactor effluent” refers to all components that can be presentin and can be removed from a trimerization reactor, including, but notlimited to, unreacted olefin, catalyst system, trimerization product(s)and/or reaction co-product(s), also referred to as reactionby-product(s). “Catalyst kill” refers to those compounds which candeactivate, either partially or completely, catalyst system used in thetrimerization process. “Heavies” refers to reaction co-product(s) whichhave a higher molecular weight than olefin reactants and/or the desiredtrimerization reaction product(s), and include higher olefinic products,such as, for example decenes and tetradecenes, as well as polymericproducts.

Referring to FIG. 1, olefin feed, and optionally hydrogen, is fedthrough inlet line 1 into trimerization reactor 4. Inlet line 2introduces catalyst system and optionally, solvent into trimerizationreactor 4. Inlet line 3, an optional embodiment of the invention, cansupply olefin feed from a second source, such as, for example anethylene effluent, or discharge, stream from a polyethylenepolymerization production facility. Trimerization reactor effluentcomprising trimerized product(s), reaction co-product(s), unreactedolefin, catalyst system, and other reactor components is removed viaeffluent line 6. Catalyst system deactivation, i.e., “kill”, components,if desired are fed via inlet line 5 into effluent line 6. It should benoted that lines 1, 2, 3, and 6 can be located anywhere on trimerizationreactor 4. However, the location of lines 1, 2, and 3 must allow olefinfeed stream to thoroughly contact catalyst system from line 2 intrimerization reactor 4. Filter 7 is an optional embodiment of theinvention which can remove particulates, such as, for example, catalystfines and undesirable polymeric products, from effluent line 6. Forexample, if the reactor effluent stream in effluent line 6 is maintainedat a higher temperature, fewer particulates, such as, for exampleparticulates resulting from undesirable polymer product(s), can form andfilter 7 may not be necessary. While not wishing to be bound by theory,it is believed that higher reactor and line temperatures can inhibitsolidification of undesirable polymer particles, i.e., highertemperatures can keep undesirable polymer particles from precipitating.However, if the reactor effluent stream in effluent line 6 is allowed tocool and particulates can form, filter 7 can be used. Line 8 can beeither filter 7 effluent or a continuation of effluent line 6 and line 8comprises little or no particulates. Inlet line 9 is a further optionalembodiment of the invention and can include a stream of heavies to beseparated, such as, for example a discharge effluent stream from apolyethylene production plant. Separator 10 separates catalyst systemand other heavies from lighter olefins. Effluent line 12 is an effluentstream comprising catalyst system and other heavy olefins from separator10. Effluent line 11 also is an effluent stream from separator 10 andcan be used to recover light olefins, including trimerized products.Separator 13 can be used to separate trimerized products from olefinreactants via effluent line 14 and solvent via effluent line 15.Separator 16 can be used to separate desired trimerization product(s)via effluent line 17 from trimerization reaction solvent via effluentline 18. Separator 19 can be used to separate trimerization reactionsolvent via effluent line 20 for reuse or recycle from other componentswhich can be removed via effluent line 21.

Referring now to FIG. 2, another embodiment of the invention, whereinlike numbers represent like components, separator 22 and lines 23, 24,and 25 are added. Separator 22 can be used to separate trimerizationproduct(s) via effluent line 23 from trimerization reaction solvent viaeffluent line 24 and any other remaining reaction components viaeffluent line 25.

Referring now to FIG. 3, another embodiment of the invention, whereinlike numbers represent like components and wherein a solvent is not usedduring the trimerization process. Therefore, separator 26 is used toseparate trimerization product(s) via effluent line 27 from all otherremaining components removed via effluent line 28.

Referring now to FIG. 4, another embodiment of the invention whereinlike numbers represent like components, separator 29 is used to separateolefin feed and trimerization product(s) via effluent line 30. Ifdesired, olefin feed and trimerization product(s) can be fed directly toan olefin polymerization unit where an olefin feed and trimerizedproduct(s) are polymerized to form a copolymer, such as, or example anethylene hexene copolymer. Solvent, if present in trimerization reactor4, can be removed from separator 29 via effluent line 31. Effluent line32 removes excess and/or deactivated catalyst system and other heavieswhich can be produced during the trimerization reaction.

Referring to FIG. 5, again like numbers represent like systemcomponents, separator 33 is used to recover any unreacted olefin feedvia effluent line 34. Effluent line 35 carries all non-recovered olefinproducts to separator 37. Inlet line 36 is similar to inlet line 9 inprevious drawings wherein a stream of heavies from another location,such as, for example a polyethylene plant, is added for separation.Separator 37 can be used to separate trimerization product(s) viaeffluent line 38, solvent via effluent line 39, and catalyst and otherproducts via effluent line 40.

Referring now to FIG. 6, another embodiment of the invention, whereinlike numbers represent like components and wherein a catalyst system andheavies effluent line can be fed to separator 41 to separatetrimerization reaction by-products, such as decenes via effluent line 42from other reactor effluent components via effluent line 43, such as,for example catalyst system, polymer particulates, other higher olefinicby-products, including some decenes. It should be noted that some of thedecenes must be kept in effluent line 43 in order to maintainflowability of catalyst system effluent and/or discharge products andpossible polymer particulates, if not removed previously in filter 7.Decenes removed via effluent line 42 can be recovered or routed foradditional use, such as hydrogenation to commercially useful productssuch as Soltrol® 100.

Note that the invention is not limited only to the embodimentsspecifically shown in the figures. For example FIG. 5 shows oneseparator 37 after an olefin removal separator 33. Other variants, suchas using two separator columns to separate trimerized product(s) andsolvent, such as in FIG. 1 with separator 16 and separator 19, can beused or solvent removal may not be necessary, as shown in FIG. 3 withseparator 26.

Reaction Conditions

Reaction products, i.e., olefin trimers as disclosed in thisspecification, can be prepared with the disclosed catalyst systems bysolution reaction, slurry reaction, and/or gas phase reaction techniquesusing conventional equipment and contacting processes. Contacting of theolefin feed with a catalyst system can be effected by any manner knownin the art. One convenient method is to suspend the catalyst system in asolvent, i.e., diluent or medium, and to agitate the mixture to maintaina uniform catalyst system concentration throughout the reaction mixtureand/or maintain the catalyst system in solution throughout thetrimerization process. Other known contacting methods can also beemployed.

A trimerization process can be carried out in an inert solvent, such asa paraffin, cycloparaffin, or aromatic hydrocarbon. Exemplary reactordiluents include, but are not limited to, isobutane, cyclohexane andmethylcyclohexane. Isobutane can be used to improve processcompatibility with other known olefin production processes. However, ahomogenous trimerization catalyst system can be more soluble incyclohexane. Therefore, a preferred solvent for a homogeneous catalyzedtrimerization process is cyclohexane.

Alternatively, a “solventless” reaction system can be used. In asolventless system, reaction product can be the reactor “solvent” ordiluent. For example, if ethylene is trimerized to 1-hexene, 1-hexenecan be used in the reactor as a solvent, or diluent. A solventlessreaction system is preferred in that fewer separation steps can be usedfollowing completion of the trimerization reaction.

Reaction temperatures and pressures can be any temperature and pressurewhich can trimerize the olefin reactants. When the reactant ispredominately ethylene, a temperature in the range of about 0° to about300° C. (about 32° to about 575° F.) generally can be used. Preferably,when the reactant is predominately ethylene, a temperature in the rangeof about 60° to about 275° C. (about 140° to about 530° F.) is employed.Most preferably, reactor temperature is within a range of 110° to 125°C. (235° to 255° F.). Reactor temperatures that are too low can causepolymeric products to precipitate out of the process can decreaseproduct selectivity by increasing the production of polymeric products.Reactor temperatures that are too high can decrease catalyst systemactivity, negatively affect reaction selectivity and can causedecomposition of the catalyst system and reaction products. However,reactor temperature range s can vary if other solvents are used in thetrimerization process.

Generally, reaction pressures are within a range of about atmospheric toabout 2500 psig. Selection of reaction pressure depends on the solvent,or diluent, used in the reactor. Preferably, when using a diluent otherthan 1-hexene, reaction pressures within a range of about atmospheric toabout 1500 psig and most preferably, within a range of 600 to 1000 psigare employed. Preferably, when using 1-hexene as the diluent, reactionpressures within a range of about atmospheric to about 2000 psig andmost preferably, within a range of 1100 to 1600 psig are employed. Toolow of a reaction pressure can result in low catalyst system activity.

Optionally, hydrogen can be added to the reactor to enhance productselectivity, i.e., reduce formation of polymeric products.

A further understanding of the present invention and its advantages alsowill be provided by reference to the following examples.

EXAMPLES Example 1

This example shows different methods of preparing trimerization catalystsystems and the trimerization results. Runs 101–106 demonstrate catalystsystem preparation outside of the trimerization reactor and feedingcatalyst system into the trimerization reactor. Runs 107–109 demonstratea catalyst system preparation method inside the trimerization reactor.Runs 110–112 demonstrate another catalyst system preparation methodinside the trimerization reactor. All catalyst system preparation wascarried out under an inert atmosphere (nitrogen or helium) usingstandard Schlenk techniques, if applicable. All solvents, or diluents,were dried over mole sieves/alumina and purged with nitrogen before use.The components used to prepare the catalyst systems and the molar ratiosof chromium to other catalyst system components are listed in Table 1.

Catalyst systems used in Runs 101–106 were prepared by dissolvingchromium tris(2-ethylhexanoate) [Cr(EH)₃) in toluene or ethylbenzene (40ml/g Cr(EH)₃). In a separate container, triethylaluminum (TEA) and achloride source were mixed together. 2,5-Dimethylpyrrole (DMP) was addedto either the Cr(EH)₃ solution or the aluminum alkyl-chloride source.The chromium mixture, either with or without DMP, depending on thepreparation method selected above, was added to the aluminum mixture andthe resulting brown-yellow solution was stirred for a time within arange of 10 minutes to one (1) hour. The resulting solution then wasfiltered through a celite frit and was diluted to the desiredconcentration.

Catalyst systems used in Runs 107–109 were prepared by dissolvingCr(EH)₃ in cyclohexane and diluting to the desired concentration withadditional cyclohexane. This solution was charged to a catalyst feedtank to the reactor. TEA and chloride sources were mixed together in 200ml of cyclohexane. DMP was added to the aluminum alkyl/chloride sourceand allowed to react for 5 minutes. This solution, along with thesolvent for that particular run, was charged to a solvent feed tank tothe reactor. Thus, the aluminum alkyl/chloride source/DMP mixture wasfed to the reactor in the same stream as the reactor solvent, butseparately from the chromium source.

Catalyst systems used in Runs 110–112 were prepared by dissolvingCr(EH)₃ in cyclohexane and diluting to the desired concentration withadditional cyclohexane. This solution was charged to a catalyst feedtank to the reactor. TEA and chloride sources were mixed together in 100ml of cyclohexane. DMP was added to the aluminum alkyl/chloride sourceand allowed to react for 5 minutes. The resulting aluminumalkyl/chloride source/DMP solution was diluted to the desiredconcentration with additional cyclohexane and then charged an aluminumfeed tank to the reactor. Thus, the aluminum alkyl/chloride source/DMPmixture was fed to the reactor in a separate stream from either thereactor solvent or the chromium source.

All trimerization reactions disclosed in Runs 101–112 can be consideredcontinuous feed reactions, i.e., not batch reactions. The feed rates andtemperatures of all Runs are given in Table 2. Reactor volume in Runs101, 105 and 110–112 was 0.264 gallons; reactor volume in all other Runswas one (1) gallon. Reactor pressure in Run 102 was 1465 psia; reactorpressure in all other Runs was 800 psia. The temperature and pressure ofthe reactor were continuously controlled at the desired values. Reactortemperature was controlled by an internal coiled pipe. Each Run sequencewas started by turning on a solvent pump to fill the autoclave reactorand heating the reactor to the desired temperature. The reactor waspurged with the solvent shown in Table 2 for 30 minutes. Additionalprocess conditions are given in Table 1.

In Runs 101–107, catalyst system was fed to the reactor at double thedesired rate for 30 minutes prior to the introduction of ethylene andthen reduced to the desired feed rate. In Runs 101 and 103–106, solventfeed continued during catalyst system feed and ethylene/hydrogen mixturefeed. In Run 102, 1-hexene was fed with catalyst system until theaddition of the ethylene/hydrogen mixture; 1-hexene feed was stoppedwhen the ethylene/hydrogen mixture feed began.

In Runs 107–109, two different reactor inlets simultaneously fed a) acatalyst system portion comprising a Cr(EH)₃ solution and b) solvent andanother catalyst system portion comprising an aluminum alkyl/chloridesource/DMP solution.

In Runs 110–112, three different reactor inlets simultaneously fed a) acatalyst system portion comprising a Cr(EH)₃ solution, b) anothercatalyst system portion comprising an aluminum alkyl/chloride source/DMPsolution, and c) solvent.

Upon exit from the reactor, the catalyst/product solution stream wasdeactivated with an alcohol, cooled and filtered in a pressure vesselthrough a steel sponge filter material to remove polymeric solids. Theproduct stream was taken to a product storage tank.

Each reaction was monitored for 6 hours. On-line samples were collectedonce every hour and analyzed by gas chromatography to determine reactoreffluent composition. Product analyses are given in Table 2.

TABLE 1 Catalyst Components and Process Conditions Solvent H₂ ReactorCatalyst Catalyst Al Feed C₂ = Feed Feed Feed Moles/mole Cr ChlorideTemp, Concent. Feed Rate, Rate, Rate, Rate, Rate, Run DMP TEA ChlorideSource Solvent ° C. MgCr/ml ml/hr ml/hr g/hr gallons/hr l/hr 101 3.011.0 8.0 DEAC Isobutane 100 0.35 45 — 275 0.60 4.40 102 1.8 9.0 2.5 EADCl-Hexene 115 0.50 30 — 1570 0.00 15.7 103 1.8 6.5 5.0 DEAC Cyclohexane115 0.80 30 — 1430 1.20 5.20 104 3.0 11.0 8.0 DEAC Cyclohexane 115 0.1730 — 1450 1.35 4.10 105 3.0 11.0 8.0 DEAC n-Heptane 120 0.25 30 — 5600.50 3.10 106 3.0 11.0 8.0 DEAC Methyl- 128 1.01 45 — 1640 1.35 8.20cyclohexane In-situ —Al in solvent 107 3.0 11.0 8.0 DEAC Cyclohexane 1150.33 30 — 1430 1.20 5.20 108 3.0 19.0 1.3 C2C16 Cyclohexane 115 0.33 30— 1430 1.20 5.20 109 16.0 50.0 63.0 DEAC Cyclohexane 115 0.04 30 — 14301.20 5.20 In-situ —Al in Tank 110 3.0 11.0 8.0 DEAC Cyclohexane 120 .2925 25 550 0.40 3.10 111 3.0 11.0 8.0 DEAC Cyclohexane 120 .29 25 25 5500.40 3.10 112 3.0 11.0 8.0 DEAC Cyclohexane 120 .29 25 25 550 0.40 3.10

TABLE 2 Product Analysis (weight percents) % Productivity, Productivity,% % Internal Hexene % % % Ethylene Polymer g olefin/g g olefin/g RunButenes l-Hexene Hexenes Purity, % Octenes Decenes Conversion Produced,g Cr-hr Metals - hr 101 <0.1 93.7 1.4 98.6 0.3 4.6 42.3 0.4 7000 640 1020.4 88.8 0.8 99.1 0.5 8.8 78.1 2.9 71800 10300 103 0.1 84.5 0.7 99.2 0.213.3 86.6 2.4 43400 6220 104 0.1 94.1 0.4 99.6 0.3 5.1 68.0 1.6 18500017000 105 0.1 91.8 0.8 99.1 0.3 6.7 72.0 0.4 49300 4540 106 0.3 85.0 1.598.3 0.4 11.9 83.2 1.1 25600 2350 107 0.1 92.1 0.4 99.6 0.3 6.8 75.9 2.5101000 9300 108 0.2 79.9 1.5 98.2 0.4 16.4 89.9 1.1 104000 9550 109 0.196.2 0.6 99.6 0.3 3.1 47.2 1.0 533000 8940 110 0.2 91.5 0.6 99.3 <0.17.2 76.5 0.1 52300 4810 111 0.2 93.0 0.6 99.3 0.1 5.6 74.9 0.3 520004790 112 0.2 92.5 0.7 99.3 0.2 6.1 74.6 0.1 51500 4740

Example 2

These examples demonstrate the process of trimerizing ethylene to make1-hexene and the separation steps necessary to produce the desiredproduct purity.

Greater than 98.5% purity 1-hexene was produced in Runs 201–203 in thefollowing manner. Ethylene and catalyst system were fed to a reactor inthe presence of a diluent/solvent. The reactor effluent was stripped ofethylene in column 1. Subsequently, 1-hexene product was removed fromthe diluent/solvent, spent catalyst, and other heavier co-products incolumn 2. Finally, spent catalyst and other heavies were removed fromthe diluent/solvent in column 3. The diluent/solvent then was returnedto the reactor.

The reactor was liquid full and had a volume of 10 gallons. Columns 1,2, and 3 were packed towers. The diluent/solvent was methylcyclohexane.The reactor pressure used was 800 psig (5516 Kpa).

Run 201

The catalyst system was prepared in the same manner as described inExample 1.

To produce 1-hexene, ethylene and methylcyclohexane were fed to thereactor at a rate of 34.9 lbs/hr and 66.7 lbs/hr average, respectively.Hydrogen was added at an average rate of 3.4 standard cubic feet perhour. Catalyst was metered into the reactor at an average rate of 256ml/hr. The reactor temperature was 244 F. (118 C.).

At the conditions specified, 1-hexene product was removed from column 2at an average rate of 24.9 lbs/hr. Product purity was 98.8 weightpercent 1-hexene, with off hexenes being the other major components.Overall, selectivity of ethylene to 1-hexene was 85.9 weight percent.

Run 202

Catalyst system was prepared in the same manner as described in Example2.

Ethylene and methylcyclohexane were fed to the reactor at a rate of 49.9lbs/hr and 118.8 lbs/hr average, respectively. Hydrogen was added at anaverage rate of 4.1 standard cubic feet per hour. Catalyst was meteredinto the reactor at an average rate of 230 ml/hr. Reactor temperaturewas 247° F. (120° C.).

At the conditions specified, 1-hexene product was removed from column 2at an average rate of 31.1 lbs/hr. Product purity was 99.1 weightpercent 1-hexene, with off-hexenes being the other major components.Overall, selectivity of ethylene to 1-hexene was 92.1 weight percent.

Run 203

The catalyst system was prepared in the same manner as described inExample 1.

Ethylene and methylcyclohexane were fed to the reactor at a rate of 65.2lbs/hr and 176.3 lbs/hr average, respectively. Hydrogen was added at anaverage rate of 6.4 standard cubic feet per hour. Catalyst was meteredinto the reactor at an average rate of 285 ml/hr. Reactor temperaturewas 264° F. (129° C.).

At the conditions specified, 1-hexene product was removed from column 2at an average rate of 37.7 lbs/hr. Product purity was 99.3 weightpercent 1-hexene, with off-hexenes being the other major components.Overall, selectivity of ethylene to 1-hexene was 94.4 weight percent.

Example 3

This example shows that coproducts of the trimerization reaction, whichinclude decenes, can be hydrogenated and incorporated into commerciallyuseful and available solvents, such as Soltrol® 100. Soltrol® 100 is aregistered trademark of Phillips Petroleum Company and is a mix ofC₉–C₁₁ isoparaffins. One embodiment of such a hydrogenation process isshown in FIG. 6.

Catalyst activation and hydrotreatment were done in a downflow 2′×¾″ ODfixed-bed reactor. The reactor was charged with 15 ml of 3 mm glassbeads, 20 ml of commercially available Englehard Ni5254, lot HE 38hydrogenation catalyst, and topped with Alcoa alumina A201. Heat controlwas accomplished in a 3-zone tube furnace. Catalyst activation was doneat 343° C. with 300 cc/min of hydrogen (H₂, 99.9%) for three hours priorto hydrogenation of a decene isomer fraction of the trimerizationreaction co-product.

A decene isomer fraction of the trimerization reaction co-product, washydrotreated as it was feed to the reactor by a syringe pump. Hydrogenwas provided to the top of the reactor through a calibrated mass flowcontroller at 100 cc/min. Total pressure of 400 psig to the system wasmaintained at the reactor exit by a Moore regulator. Samples wereperiodically analyzed for bromine number and analyzed by GC and UV.

Hydrotreatment proceeded smoothly with 100% reduction of the decene todecane isomers at 1 liquid hourly spaced velocity (LHSV), 150° C., 400psig hydrogen. However, when the LHSV was raised to 3, 150° C. and 400psig H₂, total decene isomer conversion dropped to 76%. Increasing thereactor temperature to 200° C. increased conversion to 83%. Completedecene isomer conversion resulted again when the 1 LHSV, 150° C., 400psig H₂ conditions were used. As is normal for hydrotreating reactions,a heat rise was noted across the reactor which was LHSV dependent. At 1LHSV, the heat rise was 35° C.; at 3 LHSV the heat rise was 47° C.Conversion results were confirmed by GC, GC/MS and bromine numberanalysis. The results of these hydrogenations are listed below in Table3.

TABLE 3 % Reduction, Reactor H₂ Pressure, Heat Decenes to Run LHSV Temp,° C. psig Rise, ° C. Decanes 301 1 150 400 35 100 302 3 150 400 47 76303 3 200 400 47 83 304 1 150 400 35 100

A commercially available Soltrol® 100 sample, that had been hydrotreatedwas used to prepare blends stocks with the above hydrotreated product.Blends of C₁₀/Soltrol® 100 were made in 2, 10, 20, 30 and 50 volumepercent concentrations to evaluate the compatibility of these twoproducts. GC analysis, using a column that separates according toboiling points, show that the decane isomers fit into the Soltrol® 100boiling point range. The Soltrol® 100 purity was not reduced by theaddition of the hydrotreated decene product.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

1. A process for making an olefin trimerization product comprising: a)introducing an olefin feedstock and hydrogen into a reactor; b)separately introducing a catalyst system comprising a chromium source, apyrrole-containing compound, and a metal alkyl into the reactor, therebycontacting the olefin feedstock and the catalyst system in the reactor;maintaining the olefin feedstock and the catalyst system underconditions to produce a reactor effluent comprising the olefintrimerization product and reactor products; and separating the olefintrimerization product from the reactor effluent.
 2. The processaccording to claim 1, wherein the contacting of the olefin feedstock andthe catalyst system is conducted in the presence of a diluent.
 3. Theprocess according to claim 2, wherein the diluent is selected fromparaffin, cycloparaffin, an aromatic hydrocarbon, isobutane,cyclohexane, methylcyclohexane, isobutene, 1-hexene, or any combinationthereof.
 4. The process according to claim 2, wherein the olefinfeedstock and the catalyst system are maintained at a pressure in therange of about atmospheric to about 2000 psig when the diluent comprises1-hexene.
 5. The process according to claim 2, wherein the olefinfeedstock and the catalyst system are maintained at a pressure in therange of about 1100 psig to about 1600 psig when the diluent comprises1-hexene.
 6. The process according to claim 1, wherein the catalystsystem is present in the reactor effluent and the process furthercomprises deactivating the catalyst system in the reactor effluent priorto separating the olefin trimerization product therefrom.
 7. The processaccording to claim 1, further comprising filtering the reactor effluentprior to separating the olefin trimerization product therefrom.
 8. Theprocess according to claim 1, further comprising: heating the reactoreffluent.
 9. The process according to claim 1, further comprising:introducing heavies from a source independent of the reactor effluentinto the reactor effluent; and separating the heavies from the reactoreffluent.
 10. The process according to claim 1, wherein the catalystsystem is present in the reactor products and the process furthercomprises separating the catalyst system from the reactor products. 11.The process according to claim 1, wherein the olefin feedstock comprisesan olefinic compound which is self-reacting to trimerize or an olefiniccompound which reacts with other olefinic compounds to form aco-trimerization product.
 12. The process according to claim 1, whereinthe olefin feedstock comprises one or more olefin compounds having fromabout 2 to about 30 carbon atoms per molecule.
 13. The process accordingto claim 1, wherein the olefin feedstock and the catalyst system ismaintained at a temperature in the range of about 0° C. to about 300° C.(about 32° F. to about 575° F.).
 14. The process according to claim 1,wherein the olefin feedstock and the catalyst system are maintained at atemperature in the range of about 60° C. to about 275° C. (about 140° F.to about 530° F.).
 15. The process according to claim 1, wherein theolefin feedstock and the catalyst system are maintained at a temperaturein the range of about 110° C. to about 125° C. (about 235° F. to about255° F.).
 16. The process according to claim 1, wherein the olefinfeedstock and the catalyst system are maintained at a pressure in therange of about atmospheric to about 2500 psig.
 17. The process accordingto claim 1, wherein the olefin feedstock and the catalyst system aremaintained at a pressure in the range of about atmospheric to about 1500psig.
 18. The process according to claim 1, wherein the olefin feedstockand the catalyst system are maintained at a pressure in the range ofabout 600 psig to about 1000 psig.
 19. The process according to claim 1,wherein the catalyst system further comprises an inorganic oxidesupport.
 20. The process according to claim 1, wherein the chromiumsource of the catalyst system comprises one or more organic or inorganicchromium compounds, wherein the chromium oxidation state is from 0 to 6.21. The process according to claim 1, wherein the chromium source of thecatalyst system comprises a compound having a general formula ofCrX_(n), wherein X is the same or different and is any organic orinorganic radical and n is an integer from 1 to
 6. 22. The processaccording to claim 21, wherein X is an organic radical having from 1 toabout 20 carbon atoms per radical.
 23. The process according to claim21, wherein X is an organic radical selected from alkyl, alkoxy, ester,ketone, amido, or any combination thereof.
 24. The process according toclaim 21, wherein X is an inorganic radical selected from halides,sulfates, oxides, or any combination thereof.
 25. The process accordingto claim 1, wherein said chromium source of the catalyst systemcomprises a chromium(II) compound, chromium(III) compound, or acombination thereof.
 26. The process according to claim 1, wherein thechromium source of the catalyst system comprises a chromium(III)compound selected from chromium carboxylates, chromium naphthenates,chromium halides, chromium pyrrolides, chromium dionates, or anycombination thereof.
 27. The process according to claim 1, wherein thepyrrole-containing compound of the catalyst system is reactable with thechromium source to form a chromium pyrrolide complex.
 28. The processaccording to claim 1, wherein the pyrrole-containing compound of thecatalyst system is a pyrrole, any heteroleptic or homoleptic metalcomplex or salt containing a pyrrolide radical or ligand, or anycombination thereof.
 29. The process according to claim 1, wherein thepyrrole-containing compound is hydrogen pyrrolide (pyrrole), chromiumpyrrolide, lithium pyrrolide, sodium pyrrolide, potassium pyrrolide,cesium pyrrolide, salts of substituted pyrrolides, or any combinationthereof.
 30. The process according to claim 1, wherein the metal alkylof the catalyst system is a heteroleptic metal alkyl compound, ahomoleptic metal alkyl compound, or a combination thereof.
 31. Theprocess according to claim 1, wherein the metal alkyl of the catalystsystem is alkylaluminum compounds, alkylboron compounds, alkyl magnesiumcompounds, alkyl zinc compounds, alkyl lithium compounds, or anycombination thereof.
 32. The process according to claim 1, wherein themetal alkyl of the catalyst system is a non-hydrolyzed alkylaluminumcompound having a general formula of AlR₃, AlR₂X, AlRX₂, AlR₂OR, AlRXOR,Al₂R₃X₃, or any combination thereof, wherein R is an alkyl group and Xis a halogen atom.
 33. The process according to claim 1, wherein thechromium source, the pyrrole-containing compound, and the metal alkylare contacted in the presence of an unsaturated hydrocarbon.
 34. Theprocess according to claim 33, wherein the unsaturated hydrocarbon is anaromatic or aliphatic hydrocarbon in the form of a gas, liquid, orsolid.
 35. The process according to claim 33, wherein the chromiumsource, the metal alkyl, the unsaturated hydrocarbon, or any combinationthereof comprise a halide.
 36. The process according to claim 33,wherein the unsaturated hydrocarbon is ethylene, 1-hexene,1,3-butadiene, toluene, benzene, xylene, ethylbenzene, mesitylene,hexamethylbenzene, or any combination thereof.
 37. The process accordingto claim 1, wherein the catalyst system further comprises a halidesource.
 38. The process according to claim 37, wherein the halide sourcehas a general formula of R_(m)X_(n), wherein R is an organic orinorganic radical, X is a halide radical, and m+n is a number greaterthan
 0. 39. The process according to claim 1, wherein the chromiumsource, the metal alkyl, or both of the catalyst system comprise ahalide.
 40. In the selective conversion of olefins to olefintrimerization products a process comprising: a) introducing a feedstockcomprising olefins and hydrogen into a reactor; b) separatelyintroducing a catalyst system comprising a chromium source, apyrrole-containing compound, and a metal alkyl into the reactor, therebycontacting the feedstock and the catalyst system in the reactor; c)maintaining the feedstock and catalyst system in the reactor underconditions to produce a reactor effluent comprising unreacted olefins,olefin trimerization products, catalyst, and heavies; d) transferringreactor effluent comprising unreacted olefins, olefin trimerizationproducts, and heavies from the reactor to a first separator whereincatalyst and heavies are separated from the reactor effluent; e)removing from the first separator a first effluent stream comprising atleast catalyst and heavies; and f) removing from the first separator asecond effluent stream comprising at least unreacted olefins.
 41. Theprocess according to claim 40, wherein the reactor effluent is filteredbefore entering the first separator.
 42. The process according to claim40, wherein catalyst kill is introduced into the reactor effluent. 43.The process according to claim 42, wherein the reactor effluent isfiltered after introduction of the catalyst kill.
 44. The processaccording to claim 40, wherein heavies from a source independent of thereactor effluent are introduced into the reactor effluent beforeintroduction into the first separator.
 45. The process according toclaim 40, wherein an effluent stream comprising olefin and trimerizationproduct is transferred from the first separator to a second separatorwherein the effluent stream is separated into a predominantly olefineffluent stream and a predominantly trimerization product effluentstream.
 46. The process according to claim 45, wherein the predominantlytrimerization product effluent stream is transferred from the secondseparator to a third separator to separate remaining heavies from thepredominantly trimerization product effluent to provide a trimerizationproduct effluent stream.
 47. The process according to claim 40, furthercomprising: treating the first effluent stream by recovering a portionof heavier trimerized product.
 48. The process according to claim 40,wherein diluent is introduced into the reactor along with the catalystsystem.
 49. In the selective conversion of olefins to olefintrimerization products, a process comprising: a) introducing a feedstock comprising olefins and hydrogen into a reactor; b) separatelyintroducing a stream comprising diluent and a catalyst system comprisinga chromium source, a pyrrole-containing compound, and a metal alkyl intothe reactor, thereby contacting diluent, feedstock, and catalyst systemin the reactor; c) maintaining the feedstock and catalyst system in thereactor under conditions to produce a reactor effluent comprisingdiluent, unreacted olefins, olefin trimerization products, catalyst, andheavies; d) transferring reactor effluent comprising diluent, unreactedolefins, olefin trimerization products, and heavies from the reactor toa first separator wherein the reactor effluent is separated into 1)catalyst and heavies, 2) diluent, and 3) unreacted olefin andtrimerization products; e) removing from the first separator apredominantly catalyst and heavies stream; f) removing from the firstseparator a predominantly diluent stream; and g) removing from the firstseparator a predominantly unreacted olefin and trimerization productsstream.